Post on 23-Feb-2018
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ECOLOGY
Ecology
The study of the interactions between organisms
and the living (biotic) and non living (abiotic)
components of their environment
field named in 1866
Levels of Organization
1. Biosphere: Global ecosystem
- thin volume of Earth and its
atmosphere that supports life
- 13 mi thick
2. Landscape: mosaic of connected
ecosystems
3. Ecosystem: community of organisms
and physical factors (biotic + abiotic)
4. Community: all interacting organisms
living an area
5. Population: all members of same
species that live in one place
6. Organism: individual member of a species
- simplest level of organization
ALL ORGANISMS IN AN ECOSYSTEM ARE
INTERDEPENDENT UPON THE BIOTIC
AS WELL AS ABIOTIC COMPONENTS OF
SYSTEM.
Ecology of Organisms
The environment affects the distribution of organisms
and how organisms respond to their environments.
Habitat: place where organisms lives
Niche: role or job a species plays in its environment
Factors Affecting Organisms
A. Survival Factors
1. Biotic factors: all living components that affect
organisms
2. Abiotic factors: nonliving physical and chemical
characteristics
temperature humidity
salinity O2 conc.
sunlight amt. nitrogen
pH amt. precipitation
*** temp. change one of most important factors ***
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3. Biological Tolerances- range of conditions in which
an organism can live
Tolerance curve: graph of performance versus
environmental variable
- organisms can’t live outside their tolerance
limits
Survival Rates at Different Ages
Type I High
death after midpoint
Type II Steady
death not related to
age
Type III Low
death early on
4. Acclimation: ability of an organism to adjust their
tolerance to abiotic factors
ex: ability of organisms to adapt to life
at high sea levels (increase in RBC)
Difference between acclimation and adaptation
- acclimation occurs within lifetime of organism
- adaptation is a genetic change in a species
that occurs over many generations
5. Ability to control internal conditions
Conformers: do not regulate their internal conditions,
they change as their external environment
changes
ex: lizards, snakes
Regulators: use energy to control some of their internal
conditions over a wide variety of
environmental conditions
ex: mammals: body temperature
pacific salmon: control salt conc. in their
bodies
6. Ability to escape unsuitable conditions
Dormancy: long term state of reduced activity during
unfavorable environmental conditions
ex: bears hibernate
reptiles, amphibians: hide underground
Migration: move to a more favorable habitat
ex: birds
7. Availability of resources
Resources: energy and materials a species needs
(varies from species to species)
ex: food, energy, nesting sites,
water, sunlight, etc.
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Ecological Niche: the sum total of an organism’s use of abiotic/biotic resources in the environment
habitat = address vs niche = job
Includes:
- Range of conditions species can
tolerate
- Methods of obtaining needed
resource
- Number of offspring
- Time of reproduction
- All other interactions with
environment
Types of Niches
Fundamental niche:
full range of conditions and
resources that species can
potentially occupy and use
- broad range
Realized niche: range of
conditions and resources a
species actually uses
- much narrower range than
fundamental
Niche Differences
Generalists: species with broad niches,
can tolerate large range of conditions and
resources
ex: Virginia opossum- feeds on anything
Specialists: species have narrow niches
ex: panda- eats only eucalyptus trees
COMMUNITY ECOLOGY
Characterizing a Community
• Community Structure
• Species diversity: # different species
• Composition
• Dominant species
• Most abundant species or highest biomass (total wt.)
• Keystone species
• Foundation species
• Succession
The nature of a community is determined by the interactions
(symbioses) of the populations that inhabit it.
Major Types of Symbioses
1. Predation: - powerful force - regulates population size
(+/-) - influences where and how species lives by
relationship in the food web
- predator captures, kills, and consumes prey
- natural selection: favors adaptations of
predators to kill prey and avoid being
captured
ex: rattlesnakes- acute sense of
smell and heat sensitive pits
allow it to find prey even in
dark
spiders: webs
tiger’s coat: camouflage
Predation defense mechanisms
a. Mimicry:
- harmless species resembles poisonous or distasteful sp.
- two poisonous or distasteful species look alike
- Batesian mimicry- harmless sp. mimics harmful
- Mullerian mimicry – two or more harmful sp. look like
each other
b. Camoflage
Batesian Mullerian cryptic coloration
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Predation Defense Mechanisms
c. Aposematic coloration - warning coloration
(poisonous or venomous species)
Predation Defense Mechanisms
d. Herbivory-plants develop adaptations to prevent being
eaten
- physical defenses: sharp thorns, tough
leaves, spines, etc.
- secondary compounds: poisonous,
irritating, bad tasting
ex: poison ivy, oak
Types Symbioses, cont.
2. Parasitism: species interaction where one individual is
harmed and one benefits
(+/-) - parasite feeds on host
- does not immediately cause death of prey
- have adaptations to efficiently exploit host
two types
ectoparasites: external, live on host not inside
ex: fleas, lice , leeches, mosquitoes
endoparasites: internal
ex: bacteria, protists, worms
3. Competition: two species competing for the same resource:
(-/-) food, space, shelter, mate, ecological status
- Intraspecific: same species in same ecological area
ex: trees competing for light
- Interspecific: different species in same ecological area
ex: lions and tigers for similar prey.
farm of rice paddies with weeds growing in the field.
Competitive Exclusion
Two similar species cannot occupy same niche
One species outcompetes the other, eliminating it from niche
Asian bighead carp kudzu
Resource Partitioning
Each species only uses one part of available resources
Reduces competition through creation of microhabitats
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Types Symbioses, cont.
4. Mutualism and Commensalism
Mutualism: cooperative relationship where both species
benefit (sometimes one can’t live without
other) (+/+)
ex: pollination
Commmensalism: one species benefits and other is not
affected (+/0)
ex: sailfish on sharks
Properties of Communities
•Characteristics
- Species richness: number of
species in a community
- Species diversity: richness
combined with relative
abundance of each species
(how many species are
present but also how evenly
distributed the numbers of
each species are )
greater diversity = greater stability
Greater biodiversity offers:
•more food resources
•more habitats
•more resilience in face of
environmental change
Simpson Diversity Index
Species diversity: combination of richness and evenness
•Ecosystems above have
exactly the same species
richness
•Ecosystem A more even
make up than ecosystem B
D = diversity index
N = total number of
organisms of all species
n = number of individuals
of a particular species
Simpson Diversity Index
higher index =
more stable
ecosystem
Patterns of Species Richness
1. Latitude
closer to equator=more species
ex: tropical rain forests contain
most variety of species
(stable environment, year
round photosynthesis)
2. Species- area effect
larger area = more species
- Smaller geographical areas can’t
support as many species
(reduced biodiversity)
Biodiversity Depletion
Reduction of loss of plant and animal species
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Impacts of Biodiversity Loss Properties of Communities, cont.
3. Species interactions: can promote species richness
- dominant species: has the highest biomass or
is the most abundant in the community
4. Community stability: resistance to change
- directly related to species richness:
species richness improves a community’s stability
Keystone Species
Species that has a disproportionately large effect on its
environment relative to its abundance
• Exerts important regulating effect on other species in
community- usually a predator
• Increases diversity in the community
• Holds ecosystem together as a functioning unit
Sea Otter- North Pacific Beaver- North America
Foundation Species
• Primary producer that provides a large portion of fixed
carbon to provide metabolic energy for an ecosystem
• Species plays major role in creating or maintaining a habitat
that supports other species
corals sawgrass whitebark pine
marine everglades Yellowstone Park
Ecological Succession
The gradual sequential re-growth of species in an area
• major environmental disturbances change communities by
removing organisms or changing resource availability
• some species flourish immediately, are then replaced by
others, which are replaced by still others
• distrubances in community release nutrients and rejuvenate
environment
Mt. St. Helens
Types of Succession
Primary:
development of a community in an
area that has not previously
supported life
- slow progression because
minerals necessary for growth
are unavailable
ex: bare rock, sand dune, volcanic
island (bacteria, lichen,
mosses make soil)
Secondary:
sequential replacement of a species
following disruption of an
existing community
- usually quicker because soil has
been left intact
- more likely result of disturbance
ex: fires, earthquakes, floods,
agriculture, urban sprawl, etc.
burning- releases nutrients from tree tissues
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Succession, cont.
Pioneer species: small fast
growing and reproducing species
well suited for invading and
occupying
a barren/disturbed habitat
- r strategists
Climax community: stable end
point in a community after a series of
predictable stages have occurred
- climax forest dominated by trees
- species mix dependent on abiotic
factors of region
- sun, temp, rainfall, soil
fertility
ECOSYSTEMS AND THE BIOSPHERE
Ecosystem
Sum of all the organisms living within its boundaries (biotic
community) + abiotic factors with which they interact
Involves two unique processes that impact ecosystem structure:
Energy flow
Chemical cycling
Energy Transfer
• Producers
- autotrophs (bacteria, protists, plants)
- add biomass (organic material) to ecosystem
- photosynthesis: terrestrial ecosystems- plants
- chemisynthesis: acquatic ecosystems:
bacteria/protists
Measuring Productivity of Producers
Primary production : amt. of light energy chemical energy
Gross primary production (GPP): total primary production in an ecosystem
Net primary production (NPP) : gross primary production minus the
energy used by the primary producers for respiration (R):
NPP = GPP – R
- amount of chemical energy available to consumers in an ecosystem
* productivity affected by: light, nutrients, temp, moisture*
COMPARATIVE NET PRIMARY PRODUCTIVITY
OF ECOSYSTEMS
• Consumers
- heterotrophs: bacteria, protists, all fungi, animals
• herbivores: eat producers (plants)
• carnivores: eat consumers
• omnivores: eat producers and consumers
• detritivores: eat “garbage” of ecosystem
(recently dead organisms, fallen leaves,
animal wastes)
- decomposers: class of detrivores that causes
decay by breaking down dead
tissues and wastes into simpler
molecules
(bacteria,fungi, worms)
* make nutrients available to autotrophs*
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Energy Flow
• energy is transferred as one organism eats another
• energy moves thru an ecosystem moving from producers to
consumers
• scientists follow the transfer of energy by trophic levels
TROPHIC LEVELS
Trophic level: organism’s position in the sequence
of energy transfers
- Amount of energy limits
number of trophic levels and
top level carnivores
3rd level
predators of herbivores
2nd level
herbivores
1st level
all producers
Feeding Relationships in Ecosystems
Food chains
- single pathway of feeding relationships
of an ecosystem
- usually too complex to be represented
by one food chain
- short food chain: low rate of energy
transfer between trophic levels
- lower trophic levels have many more
organisms than higher trophic levels
(less energy at higher levels, so supports
fewer individuals)
Food web: interrelated food chains in an ecosystem
Plants, herbivores, and carnivores
make up the food web.
** Green plants**
base of terrestial food web
*Phytoplankton**
base of marine food web
Quantity of Energy Transfers
• About 10% of total energy consumed in one trophic level is incorporated
into organisms of the next level (energy used in respiration is lost as heat)
- maintaining body temp, ability to move, and high reproductive
rate require a lot of energy leaving less for higher levels
- energy pyramids show the rate that each level stores energy as
organic material
- loss of energy limits number of top level carnivores
-
The dynamics of energy through ecosystems have important
implications for the human population
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Biological Magnification
Substances become
concentrated in tissues
or
internal organs as they
move
up the food chain
Ecosystem Recycling
Biogeochemical Cycle:
cyclical abiotic/ biotic pathway through which
water and minerals pass in an ecosystem
Water Cycle
- movement of water from reservoirs
- water availability is key factor that regulates productivity of terrestrial
ecosystems
- water found in organisms, atmosphere, bodies of water, and below
ground
- ground water: in soil or
underground rock
- processes in water cycle
a. evaporation
b. transpiration
c. precipitation
Carbon Cycle
- cyclical relationship of photosynthesis and respiration
Nitrogen Cycle
- pathway of nitrogen through an ecosystem
1. nitrogen fixation:
conversion of nitrogen gas to nitrate
- nitrogen fixing bacteria:
convert N(g) NH3 nitrite (NO2) nitrate (NO3)
2. nitrification:
bacteria take up NH3 and
oxidize it into nitrites (NO2),
and nitrates (NO3)
3. denitrification:
anaerobic bacteria break down
nitrates and release N gas
back into atmosphere
Phosphorus Cycle
1. Inorganic phosphate is then distributed in soils and water from rain and
weathering of rocks
2. Plants take up inorganic phosphate from the soil.
- consumed by animals
- returns to soil when animal dies
3. Mineralization -organic forms of phosphate in soil made available to
plants by bacteria
4. Phosphorus incorporations into sediments from soil washed into ocean